1. Field of the Invention
The present invention relates to a maintenance technique to be performed in advance of starting print process for ink jet printers having an ink circulation mechanism.
2. Description of the Background Art
In the case of an ink jet printer which prints images by ejecting ink from nozzles, when the print process has not been performed over a long time, the solvent of ink is evaporated or volatilized in the vicinity of ink jet heads so that the viscosity of ink is increased. If the viscosity of ink is increased, the print functionality cannot be fully performed. Because of this, as the need arises, a maintenance operation is performed, for example, by suctioning the ink, cleaning nozzles and so forth. However, there is a problem that a certain amount of ink is consumed by the maintenance operation of suctioning the ink, cleaning nozzles and so forth.
In this situation, conventionally, the thickened ink is recovered by applying fine vibration to the ink chamber of an ink jet head for agitating the ink to the extent that ink is not ejected from the nozzles, as the maintenance procedure in advance of the print process, as described in Japanese Patent Published Application No. 2005-41050. Such an operation of generating fine vibration is generally called a precursor operation.
Furthermore, in recent years, it is proposed to provide an ink circulation route in the body of an ink jet printer to enable ink circulation for the purpose of improving the reliability of the print process as described in Japanese Patent Published Application No. Hei 11-342634. In the case of the ink jet printer having such an ink circulation mechanism, even if a nozzle clogs up with bubbles or debris, quick recovery is possible, and the ink circulation through the ink chamber of an ink jet head serves to sweep away high viscosity ink to the ink circulation route.
When performing the precursor operation, the strength and the driving time can be determined. Appropriate strength and driving time for recovering the high viscosity ink effectively by the precursor operation are determined in accordance with experiments and so on. On the other hand, since there are a number of inks which differs in composition and characteristics, when the precursor operation which is effectively for recovering the high viscosity is performed, the printing quality may be adversely affected by the precursor operation depending upon the characteristics of ink. For example, in the case where an ink tends to generate bubbles when fine vibration is applied to the ink by the precursor operation, the ink may be ejected in an uneven manner because of the bubbles generated by the precursor operation.
Because of this, for the ink which is vulnerable to the precursor operation, it can be considered that a weaker precursor operation is performed for a shorter period than for other inks. However, while the harmful effect of the precursor operation on the printing quality can be avoided by this solution, the high viscosity ink may not sufficiently be recovered by the precursor operation.